Untethered access point mesh system and method

ABSTRACT

A technique for implementing an untethered access point (UAP) mesh involves enabling AP-local switching at one or more UAPs of the mesh. A system constructed according to the technique may include a wireless switch; an access point (AP) wire-coupled to the wireless switch; and a UAP mesh, wirelessly coupled to the AP, including a UAP with an AP-local switching engine embodied in a computer-readable medium. Another system constructed according to the technique may include an untethered access point (UAP), including: a radio; a backhaul service set identifier (SSID) stored in a computer-readable medium; an anchor access point (AAP) selection engine embodied in a computer-readable medium. In operation, the AAP selection engine may use the radio to attempt to associate with the AAP if a beaconed backhaul SSID matches the stored backhaul SSID. A method according to the technique may include beaconing with a backhaul SSID; acting in concert with an upstream switch as an authenticator for a downstream station that responds to the beacon; providing limited local switching functionality for the downstream station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Patent Application No.60/812,403, filed Jun. 9, 2006, which is incorporated by reference.

BACKGROUND

An access point (AP) is a device used by wireless clients to connect toa network. An AP functions as a standalone entity in someimplementations and functions in cooperation with distribution hardwarein other implementations. Distribution hardware may include a wirelessswitch used to manage APs and provide network-connectivity to wirelessclients. A wireless domain may refer to a group of wireless switchesthat are configured to exchange relevant information, and using thisinformation make informed decisions. A known device is a station (e.g.,a wireless AP or client device) that is part of a network wirelessinstallation.

Trapeze Networks, Inc. (Trapeze), uses a MOBILITY POINT (MP®) APs in aMOBILITY DOMAIN™ wireless domain. An MP® AP is coupled to a MOBILITYEXCHANGE® (MX®) wireless switch. Trapeze uses MOBILITY DOMAIN™ to referto a collection of MX® switches. This collection of MX® switches sharesRF environment and station association information. This information isused by the MX® switches to support features including by way of examplebut not limitation roaming, auto channel selection, rogue AP detection,intrusion detection and/or the launching of countermeasures. Someadditional details regarding the Trapeze-specific implementation isprovided by way of example but not limitation, including novel featuresthat are discussed later in this application, in the provisionalapplication to which this application claims priority.

In a typical implementation, APs are coupled to a switch via a wire.Implementations that include untethered APs (UAPs), introduce additionalconfiguration difficulties that are only recently being explored. Thisis an area that is ripe for experimentation and innovation because ithas proven challenging to find a way to scale wireless domains usingUAPs.

These are but a subset of the problems and issues associated withwireless access point authentication, and are intended to characterizeweaknesses in the prior art by way of example. The foregoing examples ofthe related art and limitations related therewith are intended to beillustrative and not exclusive. Other limitations of the related artwill become apparent to those of skill in the art upon a reading of thespecification and a study of the drawings.

SUMMARY

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools, and methods that aremeant to be exemplary and illustrative, not limiting in scope. Invarious embodiments, one or more of the above-described problems havebeen reduced or eliminated, while other embodiments are directed toother improvements.

A technique for implementing an untethered access point (UAP) meshinvolves enabling AP-local switching at one or more UAPs of the mesh. Asystem constructed according to the technique may include a wirelessswitch; an access point (AP) wire-coupled to the wireless switch; and aUAP mesh, wirelessly coupled to the AP, including a UAP with an AP-localswitching engine embodied in a computer-readable medium. The system mayor may not further include a wired backbone coupled to a wired networkincluding the wireless switch. The UAP mesh may or may not beself-healing. A spanning-tree algorithm may or may not be embodied in acomputer readable medium of the UAP mesh. The wireless switch may or maynot include an authorization engine, embodied in a computer-readablemedium, for acting in concert with an anchoring AP to authorize adownstream station. The AP-local switching engine may or may not makeuse of a station switching record (SSR) stored a the UAP.

Another system constructed according to the technique may include anuntethered access point (UAP), including: a radio; a backhaul serviceset identifier (SSID) stored in a computer-readable medium; an anchoraccess point (AAP) selection engine embodied in a computer-readablemedium. In operation, the AAP selection engine may use the radio toattempt to associate with the AAP if a beaconed backhaul SSID matchesthe stored backhaul SSID. The UAP may or may not further include abootable image stored in a computer readable medium, wherein, inoperation, the UAP boots up using the bootable image. The UAP may or maynot use regulatory domain information to ensure the UAP is operatingwithin regulatory limits before receiving a complete configuration. TheAAP selection engine may or may not listen for a beacon from an AAP thatincludes the backhaul SSID. The AAP may or may not include a backhaulSSID stored in a computer-readable medium. The AAP may or may notinclude an authentication engine embodied in a computer-readable medium,wherein, in operation, the authentication engine works in concert withupstream components to authenticate the UAP. The AAP may or may notinclude a backhaul radio; a backhaul radio and service profile stored ina computer-readable medium; wherein, in operation, when the UAP isassociated to the AAP, the backhaul radio sends messages from the UAPupstream using the backhaul radio and service profile. The AAP may ormay not be configured to anchor the UAP and a limited number ofadditional UAPs.

A method according to the technique may include beaconing with abackhaul SSID; acting in concert with an upstream switch as anauthenticator for a downstream station that responds to the beacon;providing limited local switching functionality for the downstreamstation. The method may or may not further include sending a stationswitching record (SSR) from the upstream switch to the downstreamstation; receiving the SSR from the downstream station; storing the SSRlocally and sending the SSR upstream to a next upstream hop. The methodmay or may not further include receiving in an initial configuration thebackhaul SSID; listening for a beacon with the backhaul SSID; attemptingto associate with an anchoring AP that is beaconing with the backhaulSSID; if association is successful, receiving a station switching record(SSR) from the upstream switch, storing the SSR locally, and passing theSSR upstream.

The proposed system can offer, among other advantages, improved wirelessdomain scaling capabilities. This and other advantages of the techniquesdescribed herein will become apparent to those skilled in the art upon areading of the following descriptions and a study of the several figuresof the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated in the figures. However,the embodiments and figures are illustrative rather than limiting; theyprovide examples of the invention.

FIG. 1 depicts an example of a system including an untethered accesspoint (UAP) mesh.

FIG. 2 depicts an example of a subtree of a UAP mesh.

FIG. 3 depicts a flowchart of an example of a method for linking a UAPto an anchoring access point (AAP).

FIG. 4 depicts a diagram illustrating a UAP linking to an existingwireless network.

FIG. 5 depicts an example of a system including a self-healing UAP mesh.

DETAILED DESCRIPTION

In the following description, several specific details are presented toprovide a thorough understanding of embodiments of the invention. Oneskilled in the relevant art will recognize, however, that the inventioncan be practiced without one or more of the specific details, or incombination with other components, etc. In other instances, well-knownimplementations or operations are not shown or described in detail toavoid obscuring aspects of various embodiments, of the invention.

FIG. 1 depicts an example of a system 100 including an untethered accesspoint (UAP) mesh. In the example of FIG. 1, the system 100 includes anetwork 102, a wireless switch 104, one or more APs 106-1 to 106-N(referred to collectively as APs 106), and a UAP mesh 108.

The network 102 may include an Internet protocol (IP) network. In anembodiment, the network 102 is a wired backbone to which the wirelessswitch 104 is coupled. However, the network 102 may alternativelyrepresent the network, or any other network, to which a backbone networkis coupled or which acts as an alternative to a backbone network. Thus,the network 102 could include, for example, the Internet.

The wireless switch 104 is typically wire connected to the APs 106.Thus, the “wireless” switch could be thought of, depending upon theimplementation, as a switch for wireless traffic to and/or from a wirednetwork. The wireless switch 104 is not necessarily wirelessly connectedto anything. Each of the APs 106 could be wire coupled to respectiveswitches such that each switch is wire coupled to only a single AP. So,although the one or more APs 106 is depicted as a plurality in theexample of FIG. 1, it should be understood that the number of APs perswitch is implementation- and/or embodiment-specific. An AP and thewireless switch 104 could be combined into a single device. However, inthis description, the functionality of an AP is differentiated from thefunctionality of a switch by acting as if the APs and the wirelessswitches are distinct devices.

The wireless switch 104 may or may not have all of the tools to managewireless stations and the UAP mesh locally. For example, there may beadditional management (e.g., AAA servers) further upstream from thewireless switch 104. Since it is not critical where these services takeplace beyond the wireless switch 104, for illustrative simplicity, it isassumed that the wireless switch 104 handles all of these functions,either locally or by utilizing upstream components. For this reasons,the figures (other than FIG. 1) do not depict components furtherupstream from the wireless switch 104.

Wireless data may include, by way of example but not limitation, stationassociation data and RF environment data. The station and RF data isused by the wireless switches 104 to support features including, by wayof example but not limitation, roaming, auto channel selection, rogue APdetection, intrusion detection and the launching of countermeasures. Thewireless switch 104 may share wireless data with other wireless switches(not shown).

The wireless switch 104 controls the APs 106 (and the APs in the UAPmesh 108). In an embodiment, the APs 106 include radio transmitters andreceivers (e.g., transceivers) that are used to provide wireless networkconnectivity for users and station access to the functions of thewireless switch 104. Within an IEEE 802.11 context, a station is anyIEEE 802.11 entity or the equivalent in other related standards, and itmay be roaming or stationary. It should be noted that this definitionmay include APs.

Each of the APs 106 anchors at least a portion of the UAP mesh 108 tothe wired network. The APs 106 may be treated as border devices betweenthe wireless switch 104 (or other upstream components of the system 100)and the UAP mesh 108. This enables more efficient use of wirelessresources because proxy address resolution protocol (proxy ARP) may beused to enable the APs 106 to answer ARP requests on behalf of a remotedevice (e.g., a UAP for which an AP serves as an anchor to the wirelessswitch 104).

In the example of FIG. 1, the UAP mesh 108 is intended to depict aplurality of potentially discrete APs that do not have a wiredconnection to the wireless switch 104 or to the APs 106. That is why theAPs in the wireless mesh are referred to as “untethered.” Any station inthe UAP mesh 108, whether a UAP or some other wireless station, isanchored to the wireless switch 104 by the AP 106 and zero or more UAPsthat make up a chain of nodes from the station to the AP 106. An AP thatis closer to the wireless switch 104 in the chain may be referred to asanchoring downstream stations. For any given station, the path from thestation to the wireless switch 104 may be referred to as a spanning treebecause the UAP mesh 108 should not allow loops for traffic passingbetween a station and the wireless switch 104.

When a UAP in the UAP mesh 108 is brought online, it will attempt toreach the wireless switch 104 through a path that is optimal. (Note:Although an optimal path is desired, it may or may not be accomplishedin practice, depending upon the implemented algorithm and/orenvironmental factors). There are multiple metrics for measuring thedistance of a UAP from one of the APs 106. For example, the metric maybe time. That is, the amount of time it takes for a packet to travelbetween the UAP and the AP anchoring the UAP. Although such a metric maywork fine, it will typically vary depending upon environmental factors,such as traffic congestion or degraded received signal strength. Forsimplicity, the metric used herein is the number of hops between the UAPand the anchoring AP (AAP), with the understanding that this is but oneof many potential metrics. Thus, if a UAP is one hop away from the AAP,the UAP may be referred to as a one-hop UAP. In general, a UAP may bereferred to as an N-hop UAP where the UAP is N hops from the AAP.

Advantageously, UAPs of the UAP mesh 108 may include an AP-localswitching engine embodied in a computer-readable medium. An AP-localswitching engine may make use of a station switching record (SSR) todetermine how to switch a given message unit (e.g., a packet, frame,datagram, etc.). This enables at least some traffic to be efficientlyswitched within the UAP mesh 108. Moreover, advantageously, some trafficmay be tunneled back to a switch, while other traffic is locallyswitched. Which traffic is tunneled back, and which traffic is locallyswitched, is an implementation-specific decision that becomes availableby using the teachings described herein.

It will be appreciated in light of the description provided herein thatalthough aspects of the invention are described relative to IEEE 802.11standards, and that certain embodiments have particular features thatare implemented within the 802.11 context, the invention itself is notlimited to 802.11 networks and may generally be applied to anyapplicable wireless network; and to the extent that future technologicalenhancements might obscure the distinctions between wireless switches,APs, and/or stations, the invention is understood to include componentsproviding the features of such switches, APs, and stations independentlyof how they are packaged, combined, or labeled.

In an illustrative embodiment, the UAP mesh 108 is created from aspanning tree. Each station in the UAP mesh 108 attempts to reach thewireless switch 104 along an optimal path. Assuming the optimal path ismeasured in the number of hops to the wire, if a first station's trafficpasses through a UAP and along a path from there to the wire, a secondstation's traffic that passes through the UAP will take the same pathfrom there to the wire. Since all stations take the optimal path, thestations may be represented as edge nodes of a tree where the AP at thewire is the root node. Thus, the AP mesh acts as a spanning tree foreach station. It may be noted that the spanning tree is greedy at eachnode, which naturally results in an efficient (perhaps even optimized)tree flow.

FIG. 2 depicts an example of a subtree 200 of a UAP mesh. The subtree200 includes an anchor AP (AAP) 202, and one or more UAPs 204-1 to 204-N(referred to collectively as UAPs 204). The path upstream from the AAP202 to the switch may include no hops, if the AAP 202 is a (tethered)AP; one hop, if the AAP 202 is wirelessly coupled directly to a(tethered) AP, or a chain of UAP nodes; or multiple hops, if the pathfrom the AAP 202 to the switch includes a chain of UAPs. The pathdownstream from the UAP 204-2 may include multiple jumps, as well.However, it should be noted that if the stations are not wirelesslycoupled directly to the UAP 204-2, the UAP 204-2 is actually an AAP(i.e., the UAP 204-2 would be anchoring downstream UAPs).

In the example of FIG. 2, the AAP 202 includes a backhaul radio 210 andmemory 212. The number of UAPs 204 that are anchored by the AAP 202 maybe implementation- or embodiment-specific. For example, a particularinstallation may limit the number of UAPs 204 to, e.g., five.

The backhaul radio 210 may be a radio that is dedicated to transmittingdata associated with the UAPs 204. Whether the radio is dedicated tobackhauling is an implementation-specific decision. Since there may bemultiple radio and SSID configurations per radio-profile, the radio maybe used to perform both the backhaul function and other, e.g., 802.11services. However, it is expected that many customers who implementbackhaul services will dedicate a radio to backhaul services because thebackhaul link is an important one. In an illustrative embodiment, thebackhaul radio 210 is capable of passive scan and active scan. However,it should be noted that in some implementations, best practice mayadvice against active scan. The channel and power settings are oftenhard configured so auto-tuning may not be available and may even beundesirable. The ability to change the backhaul channel and force allUAPs to do likewise without dropping any sessions would potentially makeauto-tuning more viable. The AAP 202 may or may not include one or moreradios (not shown) in addition to the backhaul radio 210.

The memory 212 includes a plurality of modules, some of which aredepicted in FIG. 2 for illustrative purposes. A processor (not shown) iscoupled to the memory 212 in a manner that is well-known in the relevantarts. The memory 212 is intended to represent any of a plurality ofknown or convenient computer-readable mediums, including non-volatilestorage, RAM, flash memory, cache, etc. Any applicable computer-readablemedium may be used.

In the example of FIG. 2, the memory 212 includes a backhaul radio andservice profile module 214, a backhaul service set identifier (SSID)216, and an authentication engine 218. The backhaul radio and serviceprofile module 214 includes data to be used in association with thebackhaul. The backhaul SSID 216 identifies the support network. Theauthentication engine 218 facilitates authentication of wirelessstations (including UAPs). In an illustrative embodiment, theauthentication engine 218 authenticates a station in concert with aswitch or other upstream component. The station or upstream componentmay assist in the authentication “on the fly” when a wireless stationattempts to associate with the AAP 202, or in advance for apre-authorized wireless station. In an embodiment that does not have (orhas more limited) centralized management, the authentication engine 218could even be configured to authenticate without the assistance of aswitch or other upstream component.

The AAP 202 may be configured to beacon the backhaul SSID 216. Theservice profile is then associated to a radio profile and AP followingknown or convenient conventions. Since backhaul services will be appliedto specific APs in at least one embodiment, general AP-configurationpolicies (such as auto-dap templates) that can apply to unspecific APsare not enabled in this embodiment. They may be enabled in otherembodiments, however.

In the example of FIG. 2, the UAP 204-2 includes a radio 220 and memory222. Details of other ones of the UAPs 204 are omitted to avoidcluttering the figure. Each of the UAPs 204 may be identical to, similarto, or different from the UAP 204-2. The radio 220 may or may not be adedicated backhaul radio. The value of making the radio 220 into adedicated backhaul radio diminishes if the UAP 204-2 is at the edge of aUAP mesh (e.g., when there are no downstream UAPs), though the value mayor may not be diminished to zero.

The memory 222 includes regulatory domain information 224, a backhaulSSID 226, a bootable image 228, and an AAP selection engine 230. Theregulatory domain information 224 provides information to the UAP aboutallowed broadcast parameters for a given region. The CLI to preconfigurea DAP for untethered operation may include the SSID of the anchor AP anda preshared key (not shown). When the UAP is configured with thebackhaul SSID 226, the regulatory domain information 224 should probablybe stored in, e.g., flash, as well (as shown). This prevents the UAPfrom operating outside of the regulatory limits before it receives itscomplete configuration from the switch. It must be clearly documentedthat when prestaging UAPs, the regulatory and antenna information iscorrect and reflects the actual deployment to avoid regulatoryviolations. The regulatory domain information may be updated with arunning configuration.

The bootable image 228 enables the UAP 204-2 to be deployed with thesame services as the AAP 202 (though performance could be adverselyimpacted by the radio link). When the UAP 204-2 is up and running, theboot configuration associated with the bootable image 228 may bechanged. When the boot configuration is changed, the UAP 204-2 must bereset for the changes to take effect. It is not always desirable toallow the boot configuration to change. For example, it is possible fora UAP to find a switch running a software version that does not supportuntethered APs. When the UAP sees than an older version of software istrying to manage it, the UAP may choose to reboot so as to protect itsuntethered-capable running image. (This may further require that theanchor AP generate a log message when a radio link is created ordestroyed so that link flapping can be identified and, hopefully,remedied.)

The AAP selection engine 230 enables the UAP 204-2 to select an AAP froma plurality of potential AAPs. Any known or convenient algorithm may beimplemented to choose an AAP. For example, the AAP may be selected bycomparing relative signal strengths and choosing the strongest.Alternatively or in addition, each AAP could broadcast an estimated timeto wire, or number of hops to wire, which the AAP selection engine 230can use to choose an optimal AAP. In a non-limiting embodiment, theimplemented algorithm is greedy at the UAP 204-2.

In a non-limiting embodiment, if the UAP 204-2 is unable to associatewith the AAP 202, the UAP 204-2 may beacon an SOS signal, including itsserial number. The beacon signal is (hopefully) received at an AP, andsent to the wired network for processing (e.g, at a wireless switch). Ifappropriate, the upstream component may provide the AAP 202 (or someother AP within range of the UAP 204-2) with data and/or instructions tofacilitate an association.

FIG. 3 depicts a flowchart 300 of an example of a method for linking aUAP to an AAP. In the example of FIG. 3, the flowchart 300 starts atmodule 302 where a UAP listens for a beacon with a correct SSID. To knowwhether an SSID is correct, the UAP must either have the SSID stored inmemory, or be informed in some other manner. The UAP will associate tothe AAP, at which point (or perhaps after authentication) the UAP willhave layer 2 connectivity to the AAP. In order for the associated radiolink to be established, the AAP acts as an anchor point and the UAP actsas a client device.

In the example of FIG. 3, the flowchart 300 continues to module 304where the AAP acts as an authenticator in concert with a switch toauthenticate the UAP. Implementation of this technique may be based onwpa_supplicant under a BSD license including minimum eap methods.Although wpa_supplicant and WPA-PSK may be used to authenticate, this isan implementation-specific choice; any known or convenient techniquethat works for the intended purpose may be used.

In the example of FIG. 3, the flowchart 300 continues to module 306where DAP operations are carried out. This may include DAP+TAPAprotocols, including optional switch-AP security. At this point, theflowchart 300 ends, though if the DAP operations end, the flowchart 300could resume at any point (i.e., module 302, 304, or 306).

FIG. 4 depicts a diagram 400 illustrating a UAP linking to an existingwireless network. The diagram 400 includes a switch 402, an AAP 404, anda UAP 406. The switch 402 may be similar to the wireless switch 104(FIG. 1). The break 408 is intended to represent the case where the AAP404 is untethered so that there are additional nodes (e.g., a tetheredAP) between the AAP 404 and the switch 402. However, in an alternative,the AAP 404 may itself be a tethered AP wire connected to the switch402. The UAP 406 is initially not linked to the AAP 404, but becomeslinked as described below.

The UAP 406 is 1) configured with a backhaul SSID. While this is not astrict requirement, it is a convenience for those who are responsiblefor installing or placing the UAP within a UAP mesh. Conceivably, theUAP could be configured to receive an SSID over the air or acquire anSSID in some other manner.

The UAP 406 is powered up and 2) listens for a beacon with a backhaulSSID. Again, this is not a strict requirement. It is believed to be moreconvenient to have the UAP 406 listen for a beacon than to have the UAPinitiate a link prior to or instead of receiving a beacon. This is atleast in part due to standard practice in 802.11 systems, though such apractice may not be prevalent or even desired in other wireless systems.

The AAP 404 3) broadcasts a beacon with the backhaul SSID. The backhaulSSID may be preconfigured at the AAP 404 or could be received at the AAP404 from the switch at boot time or after.

The UAP 406 4) attempts to associate with the AAP 404 upon matching thebroadcast backhaul SSID with the backhaul SSID stored locally. It may benoted that the backhaul SSID of the UAP 406 is assumed to be the same asthat of the broadcast backhaul SSID. However, there may be other UAPsthat are within range of the AAP 404 that have different backhaul SSIDs(perhaps associated with a different AAP). Also, a single AAP couldconceivably have multiple backhaul radios, each associated with adifferent backhaul SSID, or even a single backhaul radio associated withmultiple backhaul SSIDs.

The AAP 404 5) authenticates the UAP 406 in concert with the switch 402.The UAP 406 may be able to form a layer 2 connection with the AAP 404when it associates, but the AAP 404 will likely not allow traffic toflow upstream until authentication is complete. While this is not astrict requirement, wireless resources are often relatively scarce, so,in an effort to conserve resources in the case where the UAP 406 isunable to be authenticated, it may be desirable to restrict traffic flowuntil authentication is complete.

The switch 402 6) generates an SSR for the UAP 406. Since the AAP 404authenticates the UAP 406 in concert with the switch 402, the switch 402knows about the UAP 406. So the switch 402 is capable of producing anSSR for the UAP 406. In an embodiment, the SSR includes data associatedwith authorized stations and access control list (ACL) filters. An ACLrefers to rules that typically detail service ports or the like that areavailable on a host or other layer 3 device, each with a list of hostsand/or networks permitted to use the service. ACLs can be configured tocontrol upstream and downstream traffic. (In this context, they aresimilar to firewalls.) Typically, servers and routers have network ACLs,but in an illustrative embodiment, ACL rules are provided to APs. TheSSR enables the UAP 406 to switch at least some traffic, therebyreducing the amount of traffic that has to be switched higher upstream.Advantageously, this pushes message filtering to the edges (or root) ofthe UAP mesh.

The switch 402 7) forms a control channel 410 to the UAP 406. It shouldbe noted that the control channel 410 may simply be a virtual “tunnel”in that tables at each hop along the path to the UAP 406 identify thenext hop. This is advantageous because it avoids flooding the UAP mesh,which is wasteful of wireless resources. It should be noted that thecontrol channel 410 is not a “tunnel” in the traditional sense because atunnel is used to carry user data, which is not necessarily the casehere.

The switch 402 8) sends the SSR to the UAP 406 via the control channel410.

The AAP 404 9) unicasts the SSR to the UAP 406. In a non-limitingembodiment, this type of action actually occurs at each hop along thepath. The SSR is “unicast” because the AAP 404 knows that thedestination of the message is the UAP 406, and any other UAPs (nowshown) that are listening to the AAP 404 know the destination is notthem or downstream from them.

The UAP 406 10) receives the SSR and propagates the SSR upstream. Thatis, the SSR is stored at the UAP 406, then sent to the next hop closerto the switch 402. Traffic associated with the UAP 406 can travelupstream as the SSR is propagated.

The AAP 404 11) receives the SSR and propagates the SSR upstream. Thisoccurs at other nodes along the UAP chain up to and including theanchoring (tethered) AP.

FIG. 5 depicts an example of a system 500, including a self-healing UAPmesh. In the example of FIG. 5, the system 500 includes a switch 502, anAP 504, UAPs 506-1 and 506-2 (referred to collectively as “one-hop UAPs506”), UAPs 508-1 and 508-2 (referred to collectively as “two-hop UAPs508”), UAPs 510-1 and 510-2 (referred to collectively as “three-hop UAPs510”), a UAP 512, a station 520, and a station 522.

Initially, it is assumed that each UAP is authenticated and has a validSSR. The SSRs facilitate at least some switching capability within theUAP mesh. For example, if the station 520 sends a packet to the station522, the packet travels upstream to the UAP 508-1, then to the UAP506-1. The UAP 506-1 knows that the destination (station 522) isdownstream. Accordingly, rather than sending the packet upstream to theswitch 502, the UAP 506-1 makes use of the limited data included in theSSR to send the packet downstream to the UAP 508-2, which sends thepacket to the UAP 510-2, which sends the packet to the UAP 512, whichsends the packet to the station 522.

The UAP mesh is self-healing in that if a node goes down, only theaffected UAPs need to update. Specifically, say the UAP 510-2 goes down.(This is represented in the example of FIG. 5 by the shading of the UAP510-2.) When the UAP 510-2 goes down, it causes several problems,including 1) the station 522 is no longer associated with a UAP that canforward messages to and from the station 522; 2) the UAP 508-2 and otherupstream nodes (e.g., the UAP 506-1) have incorrect data.

Problem 1) can be remedied in the following manner.

1.1) The UAP 512 detects a link failure between itself and the UAP 510-2because, for the purpose of example, the UAP 510-2 is assumed to havegone down.

1.2) The UAP 512 establishes a link with the UAP 510-1. The new link isrepresented in the example of FIG. 5 as a dotted line 530. It may benoted that the UAP 512 may have multiple choices of UAPs, though in theexample of FIG. 5, only the available UAP 510-1 is depicted.(Presumably, if one of the two-hop UAPs 508 were within range of the UAP512, the UAP 512 would not have been linked with the UAP 510-2, which isa three-hop UAP. Accordingly, it is assumed that only the UAP 510-1 isin range of the UAP 512.)

1.3) The UAP 510-1 sends a message to the switch 502, alerting theswitch 502 that a new SSR is needed because the station 522—and anyother stations downstream from UAP 512 (not shown)—is now reachable viaa new path.

1.4) The switch 502 sends an SSR downstream to the UAP 510-1. Relevantdata from the SSR is propagated at each node, either as the SSR ispassed down or by propagation upstream from the UAP 510-1, as has beendescribed previously. Depending upon the implementation and/orembodiment, since the UAP 512 already knows about each stationassociated with it, and can update upstream routing data locally, theUAP 512 need not necessarily receive the newly sent SSR because thedownstream paths remain unbroken, and the upstream path is establishedthrough the link to the UAP 510-1.

It may be noted that part of problem 2 is already solved in addressingproblem 1. Specifically, the UAP 506-1 has been updated correctly as theSSR is propagated at each node (if applicable). However, the UAP 508-2still includes incorrect data. Problem 2 can be fully remedied in thefollowing manner:

2.1) The UAP 508-2 detects a link failure between itself and the UAP510-2.

2.2) The UAP 508-2 waits for a timeout period. Waiting for a timeoutperiod may be important for ensuring that the station 522 maintainsconnectivity with the switch 502. Specifically, if the UAP 508-2 deletesthe data associated with the UAP 510-2 (and therefore data associatedwith downstream nodes, including the UAP 512 and the station 522), andsends the update upstream, upstream nodes will also delete the data.Eventually the update will reach the switch 502, which will updaterecords to show that stations downstream from the UAP 510-2, includingthe station 522, are now disassociated. By waiting for a timeout period,the UAP 510-1 can update appropriately, before any disassociation, toensure continuous connectivity (and, e.g., a smooth handoff).

2.3) The UAP 508-2 deletes the data associated with the UAP 510-2(necessarily including data associated with the station 522). Since theUAP 508-2 waited for a timeout period, the UAP 510-1 has presumablyupdated the switch 502, and an SSR and/or other data has been propagatedalong the path between the switch 502 and the UAP 512. Accordingly, theUAP 506-1—and, more generally, all APs on the path between the UAP 512and the switch 502—will have current data. Therefore, it is notdesirable for the update from the UAP 508-2 (deleting the UAP 510-2 andnodes downstream from UAP 510-2) to be implemented at any of the newlyupdated nodes because the update will or could (depending upon theimplementation) delete good data. In an illustrative embodiment,sequence numbers for updates may be used. Specifically, the sequencenumber associated with the deletion of the data at the UAP 508-2 shouldbe before the sequence number associated with the update at the UAP510-1. In this way, when the UAP 506-1 receives an update from the UAP508-2 to delete data, the UAP 506-1 can check the sequence number of theupdate and, noticing that the sequence number is before the sequencenumber associated with the latest update, ignore the update.Advantageously, when a UAP notices that the sequence number comes beforea most recent update, the UAP can drop the old update; all upstreamnodes will have the correct data so the update need not be passedupstream.

After the UAP 512 is linked back into the UAP mesh via the link 530, theswitching functionality of the mesh is also updated. So, if the station520 sends a packet to the station 522, the packet may be sent up to theUAP 508-1, which recognizes that the station 522 is downstream. Then theUAP 508-1 sends the packet downstream to UAP 510-1, which sends thepacket to the UAP 512, which sends the packet to the station 522.

As used herein, an AP may refer to a standard (tethered) AP or to a UAP.Where a distinction should be drawn, an AP may be referred to as a“(tethered) AP” or a “UAP,” as appropriate.

As used herein, the term “embodiment” means an embodiment that serves toillustrate by way of example but not limitation.

It will be appreciated to those skilled in the art that the precedingexamples and embodiments are exemplary and not limiting to the scope ofthe present invention. It is intended that all permutations,enhancements, equivalents, and improvements thereto that are apparent tothose skilled in the art upon a reading of the specification and a studyof the drawings are included within the true spirit and scope of thepresent invention. It is therefore intended that the following appendedclaims include all such modifications, permutations and equivalents asfall within the true spirit and scope of the present invention.

1. A method, comprising: broadcasting a beacon that includes a backhaulservice set identifier (SSID) associated with a downstream station;receiving a signal from the downstream station in response to thebroadcast beacon; authenticating the downstream station in response tothe signal; and unicasting a station-switching record (SSR) to thedownstream station after the downstream station is authenticated.
 2. Themethod of claim 1, wherein the broadcasting, receiving, authenticatingand unicasting are performed by an access point (AP).
 3. The method ofclaim 1, wherein: the broadcasting, receiving, authenticating andunicasting are performed by an access point (AP), the access point is anuntethered access point (UAP).
 4. The method of claim 1, wherein: thebroadcasting, receiving, authenticating and unicasting are performed byan access point (AP), the access point is a tethered access point thatis connected to an upstream switch.
 5. The method of claim 1, whereinthe authenticating includes transmitting an identifier of the downstreamstation to an upstream switch and receiving an authentication signalfrom the upstream switch.
 6. The method of claim 1, wherein: theauthenticating includes transmitting an identifier of the downstreamstation to an upstream switch and receiving an authentication signalfrom the upstream switch, the transmitting the identifier of thedownstream station to the upstream switch is performed via a backhaulradio.
 7. The method of claim 1, wherein: the broadcasting, receiving,authenticating and unicasting are performed by an access point (AP), theauthenticating is performed via an authentication engine of the AP. 8.The method of claim 1, wherein the backhaul SSID includes a supportnetwork identifier.
 9. The method of claim 1, further comprisingreceiving the backhaul SSID from an upstream switch.
 10. An apparatus,comprising: an access point (AP) that, in use: transmits a beacon thatincludes a first service set identifier (SSID); receives a signal from adownstream station in response to the beacon, the downstream stationhaving a second SSID that matches the first SSID; authenticates thedownstream station in response to the received signal; and unicasts astation-switching record (SSR) to the downstream station after thedownstream station is authenticated.
 11. The apparatus of claim 10,wherein the AP has: a non-transitory computer-readable medium including:the first SSID; and an authentication engine configured to authenticatethe downstream station in response to the received signal.
 12. Theapparatus of claim 10, wherein the AP is further configured to connectthe downstream station to a network.
 13. The apparatus of claim 10,wherein the AP has: a backhaul radio configured to transmit anidentifier of the downstream station to an upstream switch.
 14. Amethod, comprising: listening, at an untethered access point (UAP), todetect a broadcast beacon that includes a service set identifier (SSID)matching a local SSID of the UAP; and upon detection of the broadcastbeacon that includes the SSID matching the local SSID of the UAP,sending a signal to an AAP to attempt to associate with the AAP.
 15. Themethod of claim 14, further comprising: receiving, at the UAP and afterthe AP is associated with the AAP, a station switching record (SSR) fromat least one of the AAP or an upstream switch; and locally storing theSSR in the UAP.
 16. The method of claim 14, further comprising:receiving, at the UAP and after the AP is associated with the AAP, astation switching record (SSR) from at least one of the AAP or anupstream switch; locally storing the SSR in the UAP; and transmittingthe SSR to an upstream location.
 17. The method of claim 14, furthercomprising receiving, in an initial configuration before the listening,the local SSID.
 18. The method of claim 14, further comprising forming aLayer 2 connection with the AAP.
 19. The method of claim 14, furthercomprising: receiving, at the UAP and after the AP is associated withthe AAP, a station switching record (SSR) from at least one of the AAPor an upstream switch; and locally storing the SSR in the UAP, the SSRincluding data associated with authorized stations and/or access controllist (ACL) filters.
 20. The method of claim 14, further comprisingbeaconing an SOS signal if the attempt to associate with the AAP fails.